Hydatiform Mole

Epidemiology:

• More common in Far East
• Teens, 40-50y are at higher risk

Common sites:

Gross features:

• uterus larger than expected for dates

Histologic features:

• swollen, hydropic villi
• all villi are swollen in complete mole, and in advanced complete moles, central cavitation
• some are swollen in partial mole
• trophoblastic proliferation
• diffuse, circumferential proliferation in complete mole
• slight, focal proliferation of syncitiotrophoblast only in partial mole
• cellular atypia often in complete mole
• no fetal parts or nucleated RBC’s in complete mole

Immunophenotype:

Marker:	Sensitivity:	Specificity:
P57 (neg in trophoblast and villous stroma for complete mole)

Molecular features:

• complete mole:
• 46, XX or 46, XY (paternally derived)
• partial mole:
• 69, XXY (triploid)
• occasionally tetraploid
• flow cytometry:
• triploid peak in partial mole
• diploid peak in complete mole

Other features:

• May precede choriocarcinoma (2% incidence in complete mole, rare in partial mole)
• Invasive mole occurs in 10% of complete moles
• Penetrates the uterine wall (may perforate)
• May invade uterine vessels and embolize to distant sites, but do not grow as true metastases
• Beta-HCG is greatly elevated in complete mole